Guava leaves, as most medicinal plants used in folk medicine, lack any systematic methodology needed to demonstrate genuine efficacy. The method described in this study is the first step towards establishing consumer confidence in guava preparations and demonstrates the use of HPTLC-UV to quantify the quercetin content of Psidium guajava L.leaves (quercetin content of the leaves ranged from 0.181 0.393 %) The results obtained were accurate (recovery ranged from 96 - 97.20 %) and precise (% RSD 0.856 and SD 0.01).